Fuel and air admitting valve assembly for pulse jet burners



May 24, 1966 F'. :MAG 3,252,495

FUEL AND AIR ADMTTING VALVE SSEMBLY FOR l PULSE JET BURNERS Filed Deo.19, 1955 5f Je m i /53 54 l l'", 052

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72nd@ "/f /Cer fmir/mwfy United seres Patent o J 13 claims. (cl. 15s-4)The present invention relates to pulse jet burners in general, and moreparticularly to an improved valve assembly which serves to control theadmission of fuel and air or oxygen to such burners.

It is well known that a pulse jet burner may operate with many differenttypes of fuel including fuels which react rapidly with oxygen oroxygen-containing air and fuels which are rather slow to react. Thepulse jet burner must be constructed and assembled by carefulconsideration of the characteristics of fuel which is to be used becauseonly then is the burner capable of operating with optimum etciency. Ifthe fuel reacts rapidly, the admission of fuel and air (or oxygen) mayoccur in a Vfully automatic way, i.e., there isA no need to providevalves which admit fuel and air to the intake end of the suction duct ormixer tube which delivers the mixture of fuel and oxygen into thecombustion chamber of the burner. In such instances, the burner damsdynamically in a fully automatic way so that no valves are needed foradmission of fuel and oxygen because the fuel-air mixture or theproducts of combustion are not likely to be forced back into the fuelsupply conduit. Such dynamic (valveless) damming improves ,if the pulsejet burner receives a fuel which reacts with oxygen very rapidly, i.e.,which is easy to ignite, but the situation is different if the fuel isof the slowly reacting type. A pulse jet burner which is operated withslowly reacting types of fuel cannot prevent the mixture of fuel andoxygen or the products of combustion from traveling up the fuel supplyconduit and/ or into the surrounding atmosphere so that such burnersmust be equipped with valves which control the admission of fuel andoxygen into the mixer tube of the combustion chamber. The need for suchvalves is particularly great when a pulse jet burner is started becausea cold fuel is always slower to react.

Accordingly, it is an important object of the present invention toprovide a very simple, exceptionally compact, highly reliable and fullyautomatic valve assembly which controls the admission of slowly reactingfuel and oxygen or oxygen-containing air into the mixer tube or directlyinto the combustion chamber of a pulse jet burner.

Another object of the invention is to provide a valve assembly Iof thejust outlined characteristics wherein the valves which admit fuel andoxygen are combined into a compact unit and wherein such unit may form areadily separable attachment which may be secured to the mixer tube of apulse jet burner.

A further object of my invention is to provide a pulse jet burner whichcomprises a valve assembly of the above outlined characteristics andwhich is especially suitable for use in various household appliances andapparatus, such as water heaters and the like, wherein the space is at apremium and wherein any, even smallest, savings in space are of greatadvantage.

An additional object of the invention is to provide a valve assemblywhich serves as a highly satisfactory mechanical damming device toprevent b'ackllow of fuel-air mixture or combustion products into thefuel supply conduit and/or into the surrounding atmosphere, and'which tfatter when is capable of automatically regulating the percentage offuel in the mixture in such a way that the mixture will be the burner isstarted and that the mixture will be leaner when the burner has beenheated up to normal operating temperature.

A concomitant object of the instant invention is to provide a valveassembly embodying the above outlined features and advantages andcapable of reducing noise which develops on combustion of a fuel-airmixture in the combustion chamber of a pulse jet burner.

Still another object of the' invention is to provide an attachment whichincludes a valve assembly of the above outlined characteristics andwhich is assembled with a mixer tube in such a way that the fuel isheated automatically prior to its admission into the valve assembly.

A further object of the invention is to provide a valve assembly whichmay be readily separated from the pulse jet burner and which can betaken apart so that all of its parts may be inspected, cleaned orreplaced with little loss in time and without necessitating theutilization of special tools.

With the above objects in view, one feature of the invention resides inthe provision of a pulse jet burner which comprises a combustion chamberincluding a mixer tube, a valve assembly including a rst and a secondvalve for respectively admitting fuel and oxygen to the intake end ofthe mixer tube, and a fuel supply conduit comprising an annular soundabsorbing chamber which surrounds at least a portion of the mixer tubeand which delivers fuel to the first nozzle.

ln accordance with a more specific feature of the invention, the valveassembly comprises a substantially boxshaped housing having twoapertured wall portions which constitute the seats of the valves. Eachof these valves further comprises a stop spaced from the respective seatand a diaphragm or a similar valve member which is movable between thestop and the respective seat. One of the stops may be anchored in thehousing and may comprise one or more projections which engage and holdthe other stop at a requisite distance from the respective seat.

If necessary, the valve assembly may comprise more than one oxygenadmitting valve.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved valve assembly itself, however, both as to its construction,operation and the mode of assembling the same, together with additionalfeatures and advantages thereof, will be best understood from thefollowing detailed description of certain specific embodiments withreference to the accompanying drawings, in which:

FIG. 1 is a fragmentary axial section through a pulse jet burner whichembodies one form of the improved valve assembly; and

FIG. 2 is a greatly enlarged fragmentary axial section through the valveassembly of FIG. l.

FIG. l illustrates a portion of a pulse jet burner with a singlecombustion chamber 10 one end portion of which forms a resonance duct(not shown) serving to receive and to convey gaseous products ofcombustion which develop on ignition of a fuel-oxygen mixture. The otherend portion of this combustion chamber forms a suction duct 11, alsocalled mixer tube, wherein air or pure oxygen is mixed with a suitablefuel, and the resulting mixture is thereupon ignited in the internalspace of the combustion chamber proper or in the mixer tube. Theoperation of the pulse jet burner is well known and by itself forms nopart of my invention. The burner of FIG. 1 is especially suited for usewith a slowly reacting fuel and,

therefore, the admission of fuel and oxygen to the mixer tube 11 must becontrolled by valves: in order to insure satisfactory damming, i.e., toprevent the reaction between fuel and oxygen from spreading into thefuel supply conduit. My invention relates to a novel valve assembly 15which delivers oxygen and slowly reacting fuel to the mixer tube 11 andwhich prevents the explosion from spreading into the fuel supplyconduit.

The valve assembly 15 comprises a substantially cup shaped base 16 and acupped cover 17, and these two elements together form a substantiallybox shaped valve housing which is detachably secured to and ispreferably coaxial with the mixer tube 11. The bottom wall portion 20 ofthe base 16 constitutes the valve seat of a fuel admitting valve and isprovided with a centrally located tubular extension or nipple 18 whoseinternal diameter preferably equals or approximates the internaldiameter of the mixer tube 11. The open discharge end of the nipple 18is adjacent to but is somewhat spaced from the intake end of the mixertube 11, and these parts are coaxial with each other. The bottom wallportion 30 of the cover 17 constitutes the valve seat of a first airadmitting valve, and the base 16 comprises a second annular wall portion40 forming the valve seat of a second air admitting valve. The valveseat 40 surrounds and is axially spaced from the valve seat 20, i.e.,the plane of the valve seat 40 is located between the planes of thevalve seats 20, 30.

The valve seats 20, 30, 40 are respectively provided with concentricgroups of circularly arranged apertures 21, 31, 41. In the illustratedembodiment, the apertures 21, 31, 41 are of circular outline, but it isequally possible to use apertures in the form of arcuate slots whosecenter of curvature is located on the axis of the valve assembly 15.This assembly further comprises three annular arresting members or stopsin the form of disks 22, 32, 42 which are provided in the interior ofthe valve housing and are respectively spaced from the valve seats 20,30 and 40. It will be noted that the main body portion of each of thesedisks is located in a plane parallel with but slightly spaced from theplane of the respective valve seat, and each disk is provided with aseries of circularly arranged openings 23, 33, 43 (see particularly FIG.2) which may but need not be in exact registry with the respectiveapertures 21, 31, 41. The narrow compartment between the valve seat 20and disk 22 accommodates an annular valve member 24, here shown as anelastic diaphragm whose marginal portion is guided by a cylindricalportion 20a connecting the periphery of the valve seat 20 with theinnermost portion of the valve seat 40. A second elastic valve member inthe form of a diaphragm 34 is located in the compartment between thevalve seat 30 and disk 32, and a third annular valve member in the formof an elastic diaphragm 44 is received in the compartment between thevalve seat 40 and disk 42. The marginal portion of the diaphragm 34 isguided by a cylindrical portion 30a of the valve seat 30, and a similarcylindrical portion 40a of the valve seat 40 guides the marginal portionof the diaphragm 44. Thus, each diaphragm is free to move in therespective compartment axially between a first position in which vitseals the apertures of the respective valve seat and a second positionin which it seals the openings of the respective disk. When thediaphragms 24, 34, 44 respectively seal the apertures 21, 31, 41, thecorresponding valves act as check valves and prevent the fluid or fluidscontained in the interior of the valve housing from flowing outwardly.On the other hand, when the diaphragms 24, 34, 44 seal the openings 23,33, 43, the respective valves permit entry of fuel and air into theinterior of the valve housing and into the mixer tube 11. The openings23, 33, 43 enable the pressure prevailing in the valve housing to actagainst the respective diaphragms 24, 34, 44 and to move thesediaphragms against the respective valve seats to seal the apertures 21,31, 41 when such pressure exceeds atmospheric pressure and the pressureof fuel.

The open outer e'nds of the cylindrical portions 30a, 40a arerespectively provided with radially outwardly extending flanges 51, 50which are surrounded by a clamping device including a slotted clampingring 53 and a detachable locking member 54 which engages the slottedportion of the ring 53. A sealing washer 52 is compressed between theflanges 50, 51 and extends into the interior of the channel-shapedclamping ring 53 to prevent uncontrolled communication of air betweenthe surrounding atmosphere and the-interior of the valve housing. Asbest shown in FIG. 2, the innermost portion of the sealing washer 52serves to clamp two radially outwardly extending ange-like portions 35,45 which are respectively integral with the disks 32, 42 so that thesedisks are positively held at a requisite distance from the respectivevalve seats 30, 40.

The disk 22 is held in position by a second portion of the disk 42including a series of inclined radially inwardly extending elasticprojections or lugs 46. Since one of the air admitting valves (e.g., theone including the seat 40, the disk 42 and the diaphragm 44) constitutesan optional feature of my invention, the disk 22 may be held in positionby lugs provided on the disk 32 or in another suitable way. The disk 22comprises a radially extending flange 25 which overlies a shoulder 20bprovided at the inner side of the cylindrical portion 20a, see FIG. 2,and the lugs 46 are dimensioned in such a way that they press the v ange25 against the shoulder 20b. The disk 22 further comprises a centrallylocated tubular extension or nipple 26 which is spacedly surrounded byand extends into the nipple 18 toward but somewhat short of the intakeend of the mixer tube 11. There is a smooth arcuate transition betweenthe flat portion of the disk 22 and the nipple 26. The fuel entersbetween the nipples 18 and 26 whereas the air enters through the nipple26 so that the two fluids are mixed in the tube 11 which is ofimportance because the possibility that the mixture would explode in theinterior of the valve housing is very remote. In the position of FIG. 2,the diaphragm 34 permits air to enter through the apertures 31 and to owalong the upper side of the diaphragm 34 toward and into the nipple 26to be admitted into the mixer tube 11. The diaphragm 44 prevents entryof air through the apertures 41, and the diaphragm 24 prevents entry offuel through the apertures 21. When a mixture which is admitted to thecombustion chamber 10 is ignited by a spark plug or by Contact with thehot wall of the combustion chamber, a pressure wave travels not onlyinto the resonance duct but also into the interior of the valve housingto move the diaphragms 24, 34, 44 against the respective valve seats 20,30, 40 and to thus prevent entry of air or fuel by simultaneouslypreventing escape of combustion products into the surrounding atmosphereor into a fuel supply conduit. Each such pressure wave is followed bysuction wave which is felt in the interior of the valve housing so thatthe diaphragms 24, 34, 44 are drawn against the respective disks 22, 32,42 and allow air and fuel to enter the valve assembly. The air then owsinto the compartments accommodating the diaphragms 34, 44 and thenceinto and through the nipple 26. The fuel flows through the annular gapbetween the nipples 18 and 26 and is admixed to air which iiows throughthe nipple 26.

The apertures 21 in the valve seat 20 may communicate directly with anannular manifold (not shown) provided at the discharge end of a fuelsupply conduit and surrounding the apertures 21 or, alternatively, theseapertures 21 may receive fuel through a sound absorbing chamber 60 whoseannular casing surrounds portions of the base 16 and mixer tube 11. Thischamber 60 constitutes a sound absorbing portion of the fuel supplyconduit which includes a nozzle 61 communicating with the annularinternal space of the chamber 60. The chamber 60 and the valve assembly15 preferably form a unitary attachment which may be secured to ordisconnected from the mixer tube 11. The upper shell 62 of the chamber60 surrounds the outer side of the valve seat 20 and is press-fitted orotherwise secured on the cylindrical portion 20a. The other shell 62a ofthe chamber 60 is secured to an internally threaded sleeve 63 which ispress-fitted or otherwise secured on the nipple 18 and which meshes witha second sleeve 65 provided on the mixer tube 11. Thus, the annularinternal space of the sound absorbing chamber 60 is surrounded by theparts 62, 62a, 63 which together form the casing of this chamber. Theintermeshing portions of the sleeves 63, 65 are shown at 66 and one ofthese sleeves is provided with an annular recess which receives anannular gasket 67. If the operator desires to separate the attachmentincluding the chamber 60 and the valve assembly A15 from the pulse jetburner, he merely unscrews the sleeve 63 from the sleeve 65, and thechamber 6@ may be separated from the valve assembly 15 by withdrawingthe parts 18, 20a from the parts 62, 63. The valve assembly 15 must beremoved from time to time for the purpose of cleaning.

The provision of a sound absorbing chamber 60 which is an element of thefuel supply conduit and whose annular internal space surrounds at leasta portion of the mixer tube lll'constitutes an optional feature of myinvention, especially since the valve housing 16, 17 by itself acts as asound absorbing body which is located in the path of air and fuelflowing into the mixer tube 11. As explained hereinabove, this chamber60 may be omitted if the nozzle 61 of the fuel supply conduit isreplaced by or assumes the form of a manifold which delivers fueldirectly to the apertures 21. Also, the sound absorbing chamber 6() maybe provided in the fuel supply conduit at a distance from the mixer tube11 without departing from the spirit of my invention. In suchconstruction, the nipple 18 is screwed onto or is otherwise detachablysecured to the mixer tube 11. If one of the air admitting valves iscapable of delivering sufficient quantities of air or oxygen, the otherair admitting valve may be dispensed with.

In the embodiment of FIGS. 1 and 2, the pulse jet burner serves to heatwater or another fluid medium which is caused to flow through a heatingpipe 70. This pipe is convoluted around the mixer tube 11 and around thecombustion chamber 10.

The combustion chamber may be subdivided into two or more smallerchambers, and each such smaller chamber may receive fuel and oxygen froma separate valve assembly or, alternatively, a single valve assembly mayadmit fuel and oxygen into two or more combustion chambers. Since theinner sleeve 65 forms part of the mixer tube 11, the discharge end ofthe inner nipple 26 actually extends into the intake end of the tube 11to prevent any mixing of fuel and oxygen in the valve housing. This willbe readily understood since, when the valve 20, 22, 24 admits fuel fromthe internal space of the sound absorbing housing 60, the diaphragm 24seals the openings 23 so that the fuel must liow between the nipples 18,26 and into the mixer tube. In other words, the construction of myimproved valve assembly is preferably such that the paths for fuel andoxygen cannot merge in the valve housing 16, 17 but only in the mixertube, i.e., in a part of the combustion chamber 10.

An important advantage of the feature that the sound absorbing chamber66 of the fuel supply conduit surrounds at least a portion of the mixertube 11 is that the fuel will exchange heat with the products ofcombustion prior to its entry into the combustion chamber. This resultsin an expansion and in increased kinematic tenacity of the fuel. Suchcharacteristics of the fuel are of considerable advantage in pulse jetburners which utilize a slowly reacting fuel because the operation ofthe pulse jet burner may be normalized shortly after the burner isstarted. When the burner is started, the admission of fuel isautomatically adjusted in such a way that the mixture of fuel and oxygenis fat, i.e., that the ratio of A said valve assembly fuel to air isequal to or slightly less than 1:1. Such fat mixture will react ratherrapidly even though the combustion chamber 10 is still cold and theexplosions will produce rather strong detonations. Also, such fa-tmixture is ready to be ignited at a point close to the intake end of themixer tube 11 so that this tube is heated very rapidly and itstemperature rises to normal operating temperature within a very shortinterval of time. The tube 11 then exchanges heat with the fuel in thesound absorbing chamber 60 so that the fuel expands and the mixture ofsuch fuel with 4air is leaner \=l.1 to 1.2) because a hot mixer tubewill preheat only the fuel but not the air. Such leaner mixture willtravel deeper into the mixer tube or into the combustion chamber properso that the ignition takes place at a point which is more distant fromthe valve assembly. This is of considerable advantage because the valveassembly is not overheated and remains operative for extended periods oftime. In other words, and as long as the stroke of the fuel admittingvalve member 24 remains unchanged, the percentage of fuel in the mixturewhich is admitted into the mixer tube 11 will be regulated in a fullyautomatic way starting with a fat mixture at the outset of theoper-ation and continuing with a leaner mixture when the combustionchamber is heated up to normal operating temperature at which themixture will be ignited without a spark plug or a similar igniterdevice. The valve assembly of the present invention is particularlysuited for delivering blast furnace gas and similar types of slowlyreacting fuels.

Without further analysis, the foregoing will so fully reveal .the gistof the present -invention that others can, by applying currentknowledge, readily adapt it for various applications ywithout omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic and specic aspects of thisinvention and, therefore, such adaptations should and are -intended toIbe comprehended within the meaning and range of equivalence of thefollowing claims.

What is `claimed as new and desired to be secured by Letters Patent is:

1. In a pulse jet b-urner, in combination, a combustion -chamberincluding a mixer tube having an intake end;

a valve assembly including rst and second valve means for respectivelyadmitting fuel and air to the intake end of said mixer tube, each ofsaid valve means comprising `an `apertured seat and said valve assemblyincluding an apert'ured wall portion adjacent to said intake end andconstituting the valve seat of said rst valve means; and a fuel supply`conduit comprising -an lannular sound absorbing chamber secured to saidvalve assembly and surrounding at least a portion of said mixer tube,said ksound absorbing chamber being adjacent to said apertured wallportion so that fuel flowing through said sound absorbing chamber may bedelivered to said intake end by flowing through said iapertured wallportion.

2. A combination as set forth in claim 1, wherein comprises asubstantially box-shaped housing having two lapentured wall portionswhich respectively constitute the valve seats of said valve means, eachof said valve means further comprising a stop spaced `from therespective seat .and ya valve member reciprocable between `the stop andthe respective seat, lone of said stops having a first portion securedto said valve housing and :a second portion engaging the other st-op tohold the same in requisite position with reference .to the respectivevalve seat.

3. A combination -as set Aforth in claim 2, wherein said valve housingincludes two substantially cup-shaped members each of which comprises aflange, and clamping `means connecting the flanges Iof said cup-shapedmembers to each other, said first portion of said one st-op beingreceived between said flanges and said second portion of said one stopcomprising at least one elastic projection which engages `said .otherstop.

d. A combination as set forth in claim 1, wherein said irst valve meanscomprises a stop spaced from the respective valve seat and a valvemember movable between said stop and Ithe respective valve seat, saidstop comprising a tubular extension .projecting iat least to the intakeend of said mixertube, said first valve means being arranged to admitfuel around said extension and said second valve means being arranged toadmit air through said extension so that `the `fuel and air form amixture in' the interior of said mixer tube.

5. A combination las set forth in claim 1, wherein said valve assemblycomprises .a substantially box-shaped valve housing and wherein saidvalve housing comprises a base member including said Wall portion andsecured to said mixer tube, and a cover member connected with said basemember and including a wall portion which constitutes the valve seat ofsaid second valve means.

6. A combination as set forth in claim further comprising additional airadmitting valve means having an apertured valve seat, said base membercomprising a second wall portion surrounding the valve seat of saidiirst valve means and constituting the valve seat of said additional airadmitting valve means.

7. A combination as set forth in claim 6, wherein said second valvemeans further comprises a stop located in said housing and spaced from`the respective valve seat, and a valve member movable between said stopand the valve seat of said second valve means, said base member and saidcover member being provided with radial anges, said housing comprisingclamping means connecting said anges .to each other, and said stophaving a portion received between said iianges.

l8. A combination as set forth in claim 1, for admitting oxygen andslowly reacting fuel to said combustion chamber wherein said valveassembly comprises a first and a second valve each including asubstantially cupped valve seat having a bottom wall provided with aplurality of apertures, an annular stop located between said valve seatsin the proximity of one thereof and having a plurality olf openings, andan annular valve member movable between said stop and the respectivevalve seat so as to respectively seal the apertures `and the openings inthe corresponding valve; and means connecting said valve seats with eachother so that said seats Itogether form a box-shaped housing, one ofsaid bottom walls having a tubular extension arranged to communicatewith said combustion chamber so that pressure iand suction wavesdeveloping in said chamber when the burner is in opera- Ition will befelt in said housing whereby said valve members are respec-tively movedinto `sealing engagement with the seats and with the stops of thecorresponding valves.

9. A combination as set forth in claim 1, wherein said valve -assemblycomprises a rst and a second valve each including a valve seat having atleast one aperture, a-

stop spaced from the respective valve seat and having at least oneopen-ing, and a valve member movable between the valve seat and the stopof the respective valve to alternatively seal said aperture .and saidopening, and means connecting said valves to each other so that saidseats together form =a housing and that said stops are disposed betweensaid seats, one of said seats comprising a t-ubular portion arranged tobe connected with said combustion chamber so that pressure and suctionwaves which develop in said chamber when the burner is in operation willbe felt in said housing whereby the valve members are respectively movedinto sealing engagement with the seats and with the stops of thecorresponding valves, said fuel supply conduit comprising a portioncommunicating with the aperture of one of said valve seats so that `fueldelivered by said supply conduit may liow into said housing and aroundsaid extension when the respective valve member is moved away from saidone seat.

10. A combination as set forth in claim 9, wherein said annular chamberis outwardly adjacent to and surrounds at least a portion of said onevalve seat.

11. A combination as set forth in claim 1, for admitting oxygen andslowly reacting fuel to said combustion chamber wherein said valve`assembly comprises a first and a second valve each including asubstantially cupped valve seat having a bottom wall provided with aplurality of apertures, an annular stop located between said valve seatsin the proximity of one thereof and having a plurality of openings, andan annular elastic diaphragm movable between said stopand the respectivevalve seat so as to respectively seal the apertures and the openings inthe corresponding valve; and means connecting said valve seats with eachother so that said seats together form a box-shaped housing, one of saidbottom walls having a tubular extension `arranged to communicate withsaid combustion chamber so that pressure and suction waves developing insaid chamber when the burner is in operation will be felt in saidhousing whereby said diaphragms are respectively moved into sealingengagement with the seats and with the stops of the correspondingvalves.

1'2. In `a pulse jet burner, in combination, a combustion chamber havingan intake end; a valve assembly comprising a lirst and a second valverespectively arranged to deliver fuel and oxygen to said intake end,said first valve comprising an apertured seat surrounding said intakeend and having a tubular extension substantially coaxial with andterminating close to said intake end, an annular stop adjacent to atirst side of said valve seat which faces away from said intake end andhaving at least one opening therein, said stop further having a tubularextension surrounded by said first-mentioned extension so that saidextensions together form an annular gap which communicates with saidintake end, and an annular diaphragm disposed between said valve seatand said stop and alternatively reciprocable into sealing engagementtherewith, said second valve comprising an apertured.

valve seat having an outer side surrounded by the atmosphere and aninner side, an annular stop adjacent to said last mentioned valve seatand having at least one opening therein, and an annular diaphrgamreceived between the valve seat and the stop of said second valve andmovable alternatively into sealing engagement therewith; and a fuelsupply conduit comprising a portion surrounding a second side of saidfirst mentioned valve seat which is nearer to said intake end so thatfuel delivered by said conduit may enter said first valve to ow throughsaid annular gap and into said combustion chamber when the pressure offuel in said conduit exceeds the pressure at the tirst side of saidiirst mentioned valve seat.

13. In a pulse jet burner, in combination, a combustion chamber havingan intake end; a valve assembly comprising `a first and a second valverespectively arranged to deliver fuel and oxygen to said intake end,said first valve comprising an apertured seat surrounding said intakeend and having a tubular extension substantially coaxial with andterminating close to said intake end, an annular stop adjacent to `afirst side of said valve seat which faces away from said intake end andhaving at least one opening therein, said stop further having a tubularextension surrounded by said first mentioned extension so that saidextensions together form an annular gap which :communicates with saidintake end, yand an annular diaphragm disposed between said valve seatand said stop and alternatively reciprocable into sealing engagementtherewith, said second valve comprising an apertured valve seat havingan outer side surrounded by the atmosphere and an inner side, an annularstop adjacent to said last mentioned valve seat and having at least oneopening therein, and an annular diaphragm received between the valveseat and the stop of said second valve and movable alternatively intosealing engagement therewith; and -a fuel supply conduit comprising asound absorbing chamber surrounding a second side of said firstmentioned valve seat which is nearer to said intake end so that fueldelivered by said conduit may enter said first valve to flow throughsaid annular gap and into said combustion chamber when the pressure offuel in said conduit exceeds the pressure at the irst side of said firstmentioned valve seat, said rsound absorbing chamber surrounding aportion of and being detachably secured to said valve assembly and tosaid `combustion chamber so that fuel owing through said sound absorbingchamber exchanges heat with said combustion chamber when the pulse jetburner is in operation.

References Cited by the Examiner UNITED STATES PATENTS FREDERICK L.MATTESON, JR., Primary Examiner. MEYER PERLIN, Examiner.

10 E. G. FAVORS, Assistant Examiner.

1. IN A PULSE JET BURNER, IN COMBINATION, A COMBUSTION CHAMBER INCLUDING A MIXER TUBE HAVING AN INTAKE END; A VALVE ASSEMBLY INCLUDING FIRST AND SECOND VALVE MEANS FOR RESPECTIVELY ADMITTING FUEL AND AIR TO THE INTAKE END OF SAID MIXER TUBE, EACH OF SAID VALVE MEANS COMPRISING AN APERTURED SEAT AND SAID VALVE ASSEMBLY INCLUDING AN APERTURED WALL PORTION ADJACENT TO SAID INTAKE END AND CONSTITUTING THE VALVE SEAT OF SAID FIRST VALVE MEANS; AND A FUEL SUPPLY CONDUIT COMPRISING AN ANNULAR SOUND ABSORBING CHAMBER SECURED TO SAID VALVE ASSEMBLY AND SURROUNDING AT LEAST A PORTION OF SAID MIXER TUBE, SAID SOUND ABSORBING CHAMBER BEING ADJACENT TO SAID APERTURED WALL PORTION SO THAT FUEL FLOWING THROUGH SAID SOUND ABSORBING CHAMBER MAY BE DELIVERED TO SAID INTAKE END BY FLOWING THROUGH SAID APERTURED WALL PORTION. 